Known resilient flexible shaft couplings for connection of two coupling parts can comprise at least two, preferably rubber, coupling members or bodies resilient to applied torques, of which at least one is mountable to or is mountable on a first coupling part and at least one other is mountable on or mounted to a second coupling part, and wherein the coupling members are mounted on a common connecting piece positioned so as to be freely movable relative to the coupling parts.
A coupling of this type is described in German Patent DE-PS No. 725 651. The individual resilient, rubber coupling members are vulcanized on the one hand to the driven and on the other hand to the driving half of the coupling, and with the aid of a connecting piece, again vulcanized to them, are coupled with each other.
Couplings of this type, in which the resilient rubber elements transmit forces produced by an applied torque, on account of their elastic flexibility, are very advantageous. However, centrifugal and circumferential forces occuring during operation cause the resilient rubber coupling members to be drawn together in the axial direction. Tractive forces are thus applied to both coupling parts, which can not generally follow them, to stress the resilient rubber coupling members axially in a disadvantageous way.
It is of course technically possible to construct such couplings free from axial force loads; however the structures for correct couplings of this nature are necessarily expensive. One kind of coupling, which avoids the above described difficulty, is shown in illustration 3.2.5-21 in "Coupling Atlas", A.G.T. George Thrum, publisher, 7140 Ludwigsburg, Germany 1969. This coupling comprises a pair of resilient rings, which are clamped together opposite each other. Each ring comprises an inner ring member and an outer ring member with a substantially resilient rubber circular or ring shaped coupling member positioned therebetween, wherein each ring is mounted over two concentric coupling member annular elements, which are vulcanized coaxially to a metal ring.
Even if the comparatively large expense of this coupling, particularly in the parallel twin configuration, can be justified, there remains the disadvantage that the coupling is comparatively stiff under an applied torque.